Memory safety bugs were identified in Firefox ESR 140.0, Thunderbird ESR 140.0, Firefox 140, and Thunderbird 140, some showing evidence of memory corruption. These bugs could potentially allow an attacker to execute arbitrary code with user interaction. Mozilla addressed these issues by releasing fixes in Firefox 141, Firefox ESR 140.1, Thunderbird 141, and Thunderbird ESR 140.1. The vulnerability is tracked as CVE-2025-8040 and is associated with CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer). The CVSS v3.1 base score is 8.8, with vector AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H, indicating network attack vector, low attack complexity, no privileges required, user interaction required, unchanged scope, and high impact on confidentiality, integrity, and availability.

Successful exploitation of this vulnerability could lead to arbitrary code execution in the context of the affected Firefox or Thunderbird processes. This could compromise the confidentiality, integrity, and availability of the affected system. The vulnerability is rated high severity with a CVSS score of 8.8. There are no reports of known exploits in the wild at this time.

Mozilla has released official fixes for this vulnerability in Firefox 141, Firefox ESR 140.1, Thunderbird 141, and Thunderbird ESR 140.1. Users and administrators should promptly update to these versions to remediate the vulnerability. Patch status is confirmed by the vendor advisory. No additional mitigation steps are required beyond applying the official updates.